1. Field of the Invention:
The invention relates generally to the treatment of ocular surface disease. More specifically, the invention relates to an instrument for inserting a plug in a lacrimal punctum for treatment of ocular surface disease such as Dry Eye Syndrome.
2. Description of the Related Art:
The surface of the eye and the inner surface of the eyelid are moisturized by tears constantly produced by tear glands around the eye. A tiny hole, known as the xe2x80x9clacrimal punctumxe2x80x9d, at the inner corner of each upper and lower eye lid margin drains the tears away through a duct known as the xe2x80x9clacrimal ductxe2x80x9d to maintain the proper moisture level balance of a xe2x80x9ctear filmxe2x80x9d on the surface of the eye. The tear film serves to bath and lubricate the eye through a delicate balance of an outer lipid (oily) layer, a middle aqueous (watery) layer, and an inner mucin (mucus) layer. As shown in FIG. 1 the lacrimal duct consists of the upper punctum 10, lower punctum 12, upper canaliculus 14, lower canaliculus 16, common canaliculus 18, lacrimal sac 20 and nasolacrimal duct 22. Nasolacrimal duct 22 opens into the interior nasal meatus in the nasal cavity behind nose M (shown as a dotted line).
A collection of symptoms called xe2x80x9ckeratoconjunctivitis siccaxe2x80x9d or xe2x80x9ckeratitis siccaxe2x80x9d, commonly known as xe2x80x9cDry Eye Syndromexe2x80x9d, occur when the proper moisture level is not obtained on the eye surface due to an imbalance between the quantity or quality of tears secreted by tear glands, and the quantity of tears drained through the lacrimal duct or lost through evaporation. Dry Eye Syndrome results in dry spots on the eye that cause a feeling of a dry sensation of the eyes or even a feeling of an adhesion sensation, known as xe2x80x9casthenopiaxe2x80x9d, between the eye lid and the surface of the eye. Dry Eye Syndrome can cause general discomfort, particularly when wearing contact lenses. Further, if left untreated, Dry Eye Syndrome can result in damaged tissue and possibly scarring on the cornea leading to irreversible sight threatening conditions.
Dry Eye Syndrome is easily diagnosed through well established diagnostic tests. However, there is no known cure for Dry Eye Syndrome. Several approaches to treatment of Dry Eye Syndrome are known conventionally. For example, it is known to introduce artificial tears into the eye in the form of eye drops or the like. However, artificial tears only provide temporary relief and thus must be applied at regular intervals. Also, prolonged use of artificial tears may suppress natural tear generation and thus can lead to further aggravation of Dry Eye Syndrome. Also, various surgical procedures are known for occlusion of the upper and for lower puncta to reduce or eliminate the amount of tears from draining through the lacrimal duct. Surgical procedures, such as cauterization of the puncta, and are relatively invasive and complex.
Accordingly the less invasive procedure of inserting punctum plugs has become popular. In particular, the punctum is dilated and a plug is inserted therein to occlude the punctum. A typical punctum plug includes a cylindrical or conical body, and a coaxial hole for receiving a tip of an insertion instrument to thereby permit the plug to be supported on the insertion instrument. It can be appreciated that a punctum plug is a very small device that must be precisely inserted into the punctum at the proper depth. Over insertion or under insertion can adversely affect the efficacy of the plug.
A variety of instruments are known for inserting punctum plugs. For example, Lacrimedics, Inc. sells a punctum plug preloaded on the tip of a pin stuck into a piece of foam. The pin is used to push the plug into a punctum. After the plug is properly seated, the pin is withdrawn. However, the pin must be precisely held to position the plug in a neutral position during withdrawal, i.e., it must not be canted to one side, to avoid sticking of the plug to the pin. Such precision is difficult to achieve and thus the pin often sticks to the plug enough to unseat it during withdrawal.
Another known plug insertion instrument is sold under the tradename Michalos Insertion Forceps(trademark) by Eagle Vision, Inc. of Memphis, Tenn. This instrument includes a pin arranged at one tip for supporting a punctum plug, and a gripping hook arranged on the other tip for gripping and securing the plug prior to insertion. After the plug is inserted into a punctum, the gripping hook is released so that the pin can be withdrawn from the plug. However, the pin still may stick to the plug, and the plug can be unseated during withdrawal of the pin.
A punctum plug insertion instrument sold by GWB International, Ltd. includes a trigger mechanism for releasing the plug after insertion. A main cylindrical body has a central wire extending coaxially from one end thereof. A tube is slidably positioned around the central wire. An elliptical spring has one end attached to the main body and another end attached to the slidable tube. A punctum plug is supported on the tip of the wire prior to insertion. When the punctum is properly dilated, the plug is inserted therein and the spring is squeezed to elongate in a longitudinal direction thereby sliding the tube forwardly to move the plug off of the tip of the wire. However, the complex construction of the trigger mechanism, the elliptical spring in particular, makes a poor handle that is awkward to hold and difficult to control. Furthermore, when the trigger mechanism is activated to dislodge the plug, the slideable tube tends to push the plug deeper into the punctum than desired.
U.S. Pat. No. 741,292 discloses a punctum plug insertion instrument having an elongated button as a trigger. One end of the button is fixed to a body of the device and the other end is slideable and fixed to a wire that extends from an insertion tip of the device. Deformation of the button causes the wire to retract into the insertion tip to release a punctum plug supported on an end of the wire. However, the instrument disclosed in U.S. Pat. No. 5,741,292 is relatively complex and difficult to manufacture.
Oasis sells a punctum plug insertion instrument under the tradename Soft plug(trademark) that includes two thin elongated members defining a substantially diamond shaped outboard trigger. A thin metal tube is attached to one end of the trigger and a wire extends through the tube and is anchored at the other end of the trigger. A projection is formed on each elongated member and extends toward the wire. Pressing the elongated members towards one another causes the diamond shaped trigger to increase in length thereby pulling the end of the wire into the tube. Eventually, the projections interact with the wire to bend the wire and decrease the effective length of the wire. The increase in the length of the diamond shaped trigger and the decrease in the effective length of the wire cause the end of the wire to retreat into the tube thus releasing a punctum plug supported on the end of the wire. However, the entire handle of this instrument is effectively a trigger activation mechanism for releasing the plug. Accordingly, it is difficult to perform the intricate manipulation, including rotation and axial movement, required for insertion of a punctum plug without the prematurely activating the trigger and releasing the punctum plug. Also, it is difficult to activate the trigger without disturbing the inserted plug because trigger activation requires a relatively large stroke. Further the complexity of the device renders it difficult to manufacture. The procedure for inserting a punctum plug requires intricate and delicate manipulation. It is desirable that an insertion instrument have good ergonomics and high tactile sensation and feedback. Further, a small variation in position of the handle of a micro instrument, such as a punctum plug insertion instrument, can result in relatively large insertion errors. Accordingly, the control interface is of critical importance in punctum plug insertion instruments.
It is an object of the invention to simplify the manufacture of a punctum plug insertion instrument.
It is another object of the invention to improve tactile sensation and feedback during a punctum plug insertion procedure.
It is another object of the invention to improve balance of a punctum plug insertion instrument.
It is another object of the invention to facilitate proper positioning of the operator""s fingers on a trigger device of a punctum plug insertion instrument.
It is another object of the invention to facilitate manipulation and release of a punctum plug during an insertion operation.
A first aspect of the invention is an instrument for inserting a plug into a lacrimal punctum comprising an elongated body having a first end, a second end, a handle portion, a cavity formed in the body to define a flexible portion, and an insertion portion defined on the first end. The plug insertion portion has a passage formed therethrough in communication with the cavity formed in the body. A shaft is coupled to the body and extends through the cavity formed in the body and the passage formed through the insertion portion. The shaft has a support portion defined thereon that is adapted to be received in an aperture formed in a plug. A projection extends from an inner surface of the surface that defines the cavity in the body towards the shaft. Deformation of the flexible portion causes the projection to interact with the shaft to deform the shaft and reduce the effective length of the shaft thereby causing the support portion of the shaft to move from a position in which the support portion of the shaft extends from an end of the insertion portion to a position in which the support portion is substantially contained within the insertion portion.
A second aspect of the invention is a method of forming an instrument for inserting a plug into a lacrimal punctum. The method comprises the steps of forming an elongated body having a first end, a second end, a handle portion, a flexible portion, a cavity defined in the flexible portion, and a plug insertion portion on the first end, forming a passage through the plug insertion portion and in communication with the cavity defined in the body, coupling a shaft to the body, the shaft extending through the cavity defined in the body and the passage formed through the insertion portion and the shaft having a support portion defined thereon that is adapted to be received in an aperture formed in the plug, and forming a projection extending from an inner surface of the body that defines the cavity in the body towards the shaft.